U.S. President Barack Obama telephoned the head of Medecins San Frontieres and apologized for a deadly air strike on the aid group’s hospital in Kunduz, Afghanistan, the White House said on Wednesday.

On the call with the medical charity’s president, Joanne Liu, Obama also said the U.S. investigation into the incident would “provide a transparent, thorough and objective accounting of the facts and circumstances of the incident. And that, if necessary, the president would implement changes to make tragedies like this one less likely to occur in the future,” White House spokesman Josh Earnest told reporters.